Expanding knowledge of the Rubisco kinetics variability in plant species: environmental and evolutionary trends

The present study characterizes the kinetic properties of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) from 28 terrestrial plant species, representing different phylogenetic lineages, environmental adaptations and photosynthetic mechanisms. Our findings confirm that past atmospheric CO2/O2 ratio changes and present environmental pressures have influenced Rubisco kinetics. One evolutionary adaptation to a decreasing atmospheric CO2/O2 ratio has been an increase in the affinity of Rubisco for CO2 (Kc falling), and a consequent decrease in the velocity of carboxylation (kcatc), which in turn has been ameliorated by an increase in the proportion of leaf protein accounted by Rubisco. The trade‐off between Kc and kcatc was not universal among the species studied and deviations from this relationship occur in extant forms of Rubisco. In species adapted to particular environments, including carnivorous plants, crassulacean acid metabolism species and C3 plants from aquatic and arid habitats, Rubisco has evolved towards increased efficiency, as demonstrated by a higher kcatc/Kc ratio. This variability in kinetics was related to the amino acid sequence of the Rubisco large subunit. Phylogenetic analysis identified 13 residues under positive selection during evolution towards specific Rubisco kinetic parameters. This crucial information provides candidate amino acid replacements, which could be implemented to optimize crop photosynthesis under a range of environmental conditions. Because it catalyses one of the limiting steps in photosynthesis, Rubisco has been studied intensively over several decades, resulting in significant advances in our knowledge of its properties. The present study advances our knowledge of fundamental aspects of Rubisco evolution and diversity, revealing a trend toward increased Rubisco affinity for CO 2 (K c ) and increased carboxylase catalytic efficiency (k cat c/K c ) during the evolution of land plants. This study also increases the assortment of candidate amino acid substitutions for application to Rubisco engineering strategies. Commentary: Correlating Rubisco catalytic and sequence diversity within C3 plants with changes in atmospheric CO2 concentrations